Fungicides are compounds, of natural or synthetic origin, which act to protect plants against damage caused by fungi. Current methods of agriculture rely heavily on the use of fungicides. In fact, some crops cannot be grown usefully without the use of fungicides. Using fungicides allows a grower to increase the yield and the quality of the crop and consequently, increase the value of the crop. In most situations, the increase in value of the crop is worth at least three times the cost of the use of the fungicide.
However, no one fungicide is useful in all situations and repeated usage of a single fungicide frequently leads to the development of resistance to that and related fungicides. Consequently, research is being conducted to produce fungicides and combinations of fungicides that are safer, that have better performance, that require lower dosages, that are easier to use, and that cost less.
Synergism occurs when the activity of two, or more, compounds exceeds the activities of the compounds when used alone.